In this paper we explore the basic outlines of the classification of color by the Aguaruna Jivaro, a people of the rain forests of north-central Peru.' According to the classification of Berlin and Kay (1 969)) the color vocabulary of the Aguaruna can best be classified as Stage Illa, a system which includes basic color terms for BLACK, WHITE, RED, and GRUE. This is the first such system to be described utilizing standardized eliciting materials. Furthermore, several unexpected findings make Aguaruna of particular theoretical interest, the most important of which are the following: (1) While the majority of informants tested are found to have basic terms for the categories BLACK, WHITE, RED, and GRUE [green + blue] , 3 the focal area for lexically undifferentiated GRUE differs from that predicted in Berlin and Kay (1969:17) in that it appears in blue rather than in green. This finding requires a slight modification of the proposed order by which color foci are encoded in the diachronic development of any language's color vocabulary. (2) Patterned variation reveals considerable cognitive and lexical diversity within the Aguaruna population in terms of the number of basic color categories found in any particular individual's system. While thirty-four or approximately two-thirds of the informants tested show a Stage l l l a system as described above, five informants show color vocabularies that can best be interpreted as Stage I V (with terms for BLACK, WHITE, RED, GRUE, and YELLOW), and sixteen individuals possess a Stage V color terminology (with terms for BLACK, WHITE, RED, GRUE, YELLOW, and GREEN). Nonetheless, the new categories of YELLOW and GREEN in Stage IV and V systems, respectively, are precisely those categories which Berlin and Kay predict will be added in the history of a language's development of basic color terms. Furthermore, informants exhibiting Stage I V and V systems are seen to have greater knowledge of Spanish than those with Stage I I la systems who are, for the most part, monolingual. (3) The persistence o f the extension of a term for black, bukisea, into thegreens and blues is quite similar if not identical to the extension of comparable terms in Dani, a Stage I color system (Heider 1972)) and in Binumarian, a recently described Stage l l l b The basic color categories of the Aguaruna Jivaro are described in detail, and the influence of culture contact is explored. Methodological problems and new elicitation procedures are discussed. Finally, some elaboration on and modification of the Berlin and Kay basic color term theory is suggested.